Metal casting apparatus



July 19, 1949- R. G. HARDY 2,476,296

METAL CASTING APPARATUS Filed Aug. s, 1945 RUSSELL G. HARDY Patented July 19, 1949 UNITED"` STATI-:s PATENT OFFICE METAL CASTINGAPPARATUS aussen G. Hardy, United states Navy Application August 8, 1945, Serial No. 609,706

Claims. (Cl. 22-134) (Granted under the act oi' March 3, 1883, as amended April 30, 1928; 370 0. G. 757) This invention relates to metal casting, and more particularly to an apparatus for force feeding casting material into the casting chamber.

In casting metals, in order to obtain a homogeneous casting, which will be free from defects resultingfrom incomplete feeding of the metal into the casting chamber, it is sometimes the practice to employ means whereby during the casting operation pressure will be applied to the casting material to force feed the casting material into the casting chamber. For example, a riser may be employed having suitable dimensions and location relative to the dimensions and location of the casting chamber, so that during the casting operation the hydro-static pressure of the casting material in the riser chamber will be sumcient to force feed the casting material into the casting chamber. Where, in order to obtain satisfactory feeding, it is necessary to employ feeding pressures in excess of one atmosphere, the required size of the riser chamber may become an important consideration; and it may well be impractical to make the riser chamber as large as is required.

An object of the present invention is to provide an eilicient and effective apparatus for casting metals.

A further object of the present invention is to provide an apparatus for metal casting whereby during the casting operation a high pressure feeding action will be produced without employing a large riser chamber.

In accordance with one embodiment of this invention, a metal casting mold is employed having a blind riser located therein. A quantity of a volatilizable metal is located in the riser chamber so that during the casting operation the heat of the molten casting metal will cause the volatilizable metal to be volatilized and to produce a gas pressure in the riser chamber which will effect force feeding of the casting metal into the casting chamber.

Other objects and advantages of the present invention will 'be apparent from the following the drawings, wherein:

Fig. 1 is a horizontal sectional view taken along the line I-I of Fig. 2 showing a casting mold constructed in accordance with one embodiment of this invention and having a riser chamber y formed therein and provided with a quantity of a volatizable metal; and, f

that a substantially conventional sand mold is there shown comprising an upper section or cope i and a lower section or drag 2. A vertically extending sprue passage 3 is formed in the sand l, which'i'llls the mold, and this passage connects4 at its lower end to a horizontally extending runner passage 5. The right end of the runner passage 5 connects to the base of a blind riser chamber 6. As may be seen in the drawings, the riser chamber 6 is of substantially cylindrical shape andthe upper end wall 1 of the risei charnber is curvedA to form a dome. The lower right side of the riser chamber 6 is connected to a casting chamber 8, formed in the mo1d,by a horizontally extending runner passage d, the casting chamber 8 being formed to have the desired internal configuration. The relative sizes of the several passages and chambers is of considerable importance and it is desirable that the runner passage 9 connecting the casting chamber 8 to the riser chamber 6 have a cross-sectional dimension substantially the same as or slightly greater than the cross-sectional dimension of the casting chamber 6. Similarly the cross-sectional dimension of the riser chamber 6 is selected to beas large as or slightly greater than the cross-sectional dimension of the casting chamber 8. The cross-sectional dimension of the runner passage 5, however, is made substantially smaller than the cross-sectional dimension of the runner passage 9, so that, during the casting operation, the metal in the runner passage 5 will tend to solidify substantially prior to the solidlilcation of the metal in the casting chamber 8, the runner passage 9, and the riser chamber 6. At the same time, by making the riser chamber 6 and the runner passage 9 of similar cross-sectional size to the casting chamber 8, solidication of the casting material in the runner passage 9 and the riser chamber 6 will not occur priorto solidication of the metal in the casting chamber 8.

Normally, in using a mold such as that illustrated, a quantity of the casting material is poured into the sprue passage 3, runs down the sprue passage and along the runner passage 5 and enters the riser chamber 6. The casting material then flows down the vrunner passage 9 and into the casting chamber 8. 'I'he pouring operation is conducted at such a speed that the riser chamber 6 and casting chamber 8 are substantially sage 9, the metal in the runner passage 5 will tend to solidify rst, thus, in effect, sealing the riser chamber 6, runner passage 9 and the casting chamber l from the sprue passage 3 and the outside atmosphere. The weight of the molten casting material in the riser chamber thus serves to force feed the m'etal through the runner passage 9 and into the casting chamber 8, and to maintain a constant feeding pressure.

' In some cases it has been found that becausel of the peculiar location of the casting chamber or because of the dimensions or configuration of the casting chamber, it is necessary to employ riser chambers of impractical or undesirable size in order to obtain the required gravity feeding. Also, where certain alloys or metals having relajin the riser' chamber.

tively low skin strength are used as the casting material, such as brass or bronze, ordinary atmospheric pressure feeding techniques are Wholly inadequate.

In accordance with the present invention, in order to provide a force feed at a pressure which may be far in excess of atmospheric pressure. a quantity of a metal which is volatilizable at the temperature of the molten casting material is located in the riser chamber during the preparation of the mold. In practice, a number of metals have been found to be satisfactory and the choice of a particular metal will, in general, be dictated by the casting material and the required feeding pressure. For example, in casting inedium melting point alloys such as brass or bronze, a' suitable volatilizablmetal has been found to be zinc; the zinc may be used alone or in combination with other volatilizable metals such as phosphorus. By combining several metals various rates of volatilization may be obtained. As a practical matter, it is usually desirable to employ as a volatilizable metal one which will not contaminate the casting material. For example, zinc is particularly desirable where the casting material is an alloy including as an element thereof zinc.

As shown in the drawings, a rod I0 of the volatilizable metal is located in the upper portion of the riser chamber 6 being mounted transversely thereacross. As the purpose of the invention is to attain a superatmospheric pressure at the top of the riser 6, the element must be mounted so as to be nonventilating in the sense of not functioning to produce or preserve an air passage through any skin of solidified metal formed on the walls of the riser during casting. The method of mounting here shown is merely illustrative, however, and the volatilizable metal may be suspended by wires or otherwise suitably located in the riser chamber in a manner to permit the formation of a continuous lining of solidied metal around the walls of the riser chamber.

During the casting operation, which is conducted substantially as hereinbefore described, the casting metal in the runner passage 5 will tend to solidify prior to the casting metal in the rser chamber 6, the runner passage 8 and the casting chamber 8, because of the smaller crossrLect-ional size of the runner passage 9. This effectively seals the portion of the mold to the rght of the runner passage 5, as'viewed in these drawings. from the sprue passage. At the same time. as the casting material fills the riser chamber and comes into contact with the volatllizable metal, the heat of the casting material will cause the volatilizable metal to be volatilized and the metal vapors will tend to fill the riser chamber. In the case of zinc it yhas been found that the metal vapor or gas will, upon touching the walls of the riser chamber, condense and form a skin or layer of metal thereover, thus constituting means providing an airtight compartment and preventing the escape of pressure through the sand. Depending on the cross-sectional size of the body of volatilizable material, the composition of the body, and the amountof volatilizable metal used, a vapor pressure considerably in excess of atmospheric pressure may be developed This vapor pressure will force feed the casting material through the runner passage 9 and into the casting 'chamber 8, thereafter maintaining pressure on the casting material during the solidiflcation thereof. The rate at `which pressure is developed may be controlled by a proper selection of the cross-sectional size of the volatilizable metal body in the riser ,and of the composition of the body, a larger size producing a lowerrate of volatilization.

It will be apparent that the volatilized metal striking the casting material will tend to mix with and to chill the casting material. ,Howeven by employing zinc as the volatilizable material when casting an alloy such as bronze or brass which includes zinc as an element thereof, the l zinc while tending tovchill the casting material will at the same time tend to lower the melting point of -tbe casting material, thus in large part compensating for the chilling effect and aiding in maintaining the casting material in the runner, passage 9 and riser chamber in av liquid state. With other alloys. other volatilizable metals may be used with similar results'.

It will be understood that while, in general, it .is preferred to locate the riserv chamber intermediate the casting chamber and the sprue passace. this arrangement is not prerequisite and any location of the riser-chamber which; will permit the feeding of metal from the riser to the casting chamber after the metal in the sprue 118.57- saae has solidified may be employed.

While but one embodiment of this iriventio has been shown and described, many changes'and modifications may be made therein without departing from the spirit or the scope of the present invention.

The invention shown and described herein may be manufactured or used by or for the Government of the United States of America for governmental purposes without the royalties thereon or therefor.

4What is claimed is:

1. Apparatus for casting molten metals having a volatility less than that of zinc comprising, a mold provided with a casting chamber, a blind riser chamber communicating with said casting chamber and pouring passage means communieating with said riser chamber, and a quantity of solid zinc disposed inthe said riser chamber of said mold. r

2. Apparatus for casting molten lmetals comprising, a' mold provided with abiind casting chamber, a non-vented blind riser chamber communicating with said casting chamber and pouring passage means communicating with said riser chamber, and a solid metallic substance volatile at the melting temperature of the xretal to be cast disposed in said riser chamber.vv

3. Apparatus for castihg'moltenmetaicomprising, a mold provided'with' a casting cham-ber, a non-vented blind riser chamber' having surfaces substantially impermeable to metallic vapor, communicating passage .means connecting said casting chambei and said riser chamber having relatively low freeze-off capacity and pouring passage means communicating with said riser chamber having relatively high freeze-off capacity, and solid metallic material volatile at the melting temperature of the metal to be cast disposed in the riser chamber of said mold.

4. Apparatus for casting molten metal comprising, a mold provided with a casting chamber, a non-vented blind riser chamber having surfaces substantially impermeable to metallic vapor, passage means connecting said casting chamber and said riser chamber and adapted to prolong the molten condition of the metal after pouring and passage means connecting said riser chamber with the source of said molten metal adapted to promote solidiiication of the metal after pouring, and solid metallic material volatile at the melting temperature of the metal to be cast disposed in the riser chamber of said mold.

5. Apparatus for casting molten metal com# prising, a mold provided with a casting chamber, a lblind riser chamber communicating with said casting chamber by relatively large cross-section passage means and relatively small cross-section 6 pouring passage means communicating with said rise-r chamber, and a quantity of solid metal volatile at the melting temperature of the metal to be cast disposed in the riser chamber of said mold.

RUSSELL G, HARDY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Transactions ofthe American Foundryrnens Association, 1942, pages 253 and 259. 

